This invention relates to an exposure apparatus of the type in which a light source formed by fixing a light-emitting tube in a lamp housing filled with cooling water is rotatably supported, and which can be employed for forming, for example, a phosphor screen for a color display tube.
In a conventional exposure apparatus of the kind described above, the light source is constructed by disposing a light emitting tube, with a cover having a slit opening partly, in water. Therefore, the apparent position of the light source resulting from refraction by cooling water rises from the true position of the light source, and the exposure position accuracy is undesirably reduced when a black matrix film for a color picture tube or a phosphor film for such a tube is formed, for example. In the case of producing, for instance, a dot type color picture tube, exposure is effected while the light source is rotating with its axis of rotation being the vertical center axis with respect to the panel inner surface of the picture tube, which is the exposed surface or the surface to be exposed. Since the virtual light source has a rectangle shape which is long in the direction defined by the slot in the cover, the aspect of the rising for the longitudinal axis of the light emitting tube is different from that for the transverse axis, particularly at the peripheral region of the panel. In consequence, the projected image of the light source revolves with the rotation of light source, thereby reducing exposure accuracy. If the dimensions of the light source for forming black matrix film differ from those for phosphor film, the center positions of the dots will become different from the suitable site. That is, the black matrix hole and the phosphor dot will appear,undesirably, in different positions.
The following references are cited to show the state of the art:
(1) U.S. Pat. No. 4,187,013 and PA1 (2) U.S. Pat. No. 4,206,986.